This research paper discusses the core object model for architectural design, developed in the context of the IDEA+ project. This project aims at developing an Integrated Design Environment for Architect designers, in which design tools and computational tests are gathered around and make use of a core object model. The object-oriented analysis method MERODE is used to develop this model. Due to the method's model-driven development, conceptual modelling is subdivided in an enterprise-modelling phase and a functionality-modelling phase. This structured approach has proven to be a firm base to the development of the envisaged model and enhances the model's integration in the design environment. (C) 2001 Elsevier Science Ltd. All rights reserved.